The dimerization and codimerization of .alpha.-olefinic compounds in the presence of a group VIII noble metal salt is disclosed by Alderson (U.S. Pat. No. 3,013,066). The dimerization and codimerization of alkenes and alkyl acrylates in the presence of rhodium trichloride is disclosed by Alderson et al. (J. Amer. Chem Soc. 1965, 87, 5638-5645)
Nugent et al. (J. Molecular Catalysis 1985, 29, 65-76) disclose a process for the linear dimerization of alkyl acrylates using chlorobis(ethylene)rhodium(I) dimer in combination with a Lewis acid promoter and a proton source.
Singleton (U.S. Pat. No. 4,638,084) discloses a process for dimerizing a lower alkyl acrylate or a lower alkyl methacrylate to the corresponding dialkyl hexenedioates and dialkyl 2,5-dimethylhexenedioates by contact with a catalyst prepared by reacting chlorobis(ethylene)rhodium(I) dimer and silver tetrafluoroborate.
Brookhart et al. (J. Amer. Chem. Soc. 1988, 110, 8719-8720) disclose the use of a cationic rhodium catalyst containing a pentamethylcyclopentadienyl ligand in the dimerization of ethylene to butenes.